Electrical suspension insulator with improved pin



Sept. 18, 1962 F. c. VQSE ETAL 3,054,851

ELECTRICAL SUSPENSION INSULATOR WITH IMPROVED PIN Filed June 19, 1961 United States Patent Ofifice p 3,054,851 Patented Sept. 18, 1962 3,054,851 ELECTRICAL SUSPENSION INSULATGR WITH IMPROVED PIN Fred C. Vose and Joseph Kaminski, Jiu, Baltimore, Md.,

assignors to General Electric Company, a corporation of New York Filed June 19, 1961, Ser. No. 127,775 4 Claims. (Cl. 174-196) The present invention relates to electrical insulators, and more particularly to electrical transmission line insulators of the suspension type.

In typical known suspension insulators, a steel pin is cemented into a porcelain insulator body to serve as a connecting link to additional insulator units to provide a string of insulators. A difliculty met with in such insulators under operational conditions is that corrosion of the pin occurs under the combined effects of atmospheric contaminants, and leakage current on the insulator surface, and leads to unduly shortened insulator life, not only because of breakage of the porcelain body due to such corrosion, but also and more frequently due to failure of the pin itself.

An additional problem encountered in known types of suspension insulators is the breakage to which the porcelain bodies are susceptible due to impacts on the pin embedded therein during handling, transporting, and installing procedures, the stresses caused by such impacts being transmitted through the pin to the porcelain in the region of the embedded end of the pin.

It is an object of the invention to provide an improved suspension insulator which avoids the above difficulties by simple and economical means.

It is a particular object of the invention to provide in suspension insulators of the above type an improved construction of the insulator pin which avoids the problem of pin corrosion while simultaneously protecting the porcelain body from the effects of impacts on the pin.

Other objects and advantages will become apparent from the following description and the appended claims.

With the above objects in view, the present invention relates to an electrical insulator which comprises a ceramic dielectric member having a recess, a metal pin extending at one end into the recess and joined therein to the ceramic dielectric member by cement material occupying the recess, the pin projecting outwardly of the recess beyond the surface of the cement material, and a lead collar on the pin extending from within the recess to a point on the pin substantially beyond the surface of the cement material, whereby the pin is protected from the above-described corrosion effects and the resistance of the ceramic member to mechanical impacts on the pin is substantially increased.

The invention will be better understood from the following description taken in conjunction with the accompanying drawing, in which:

The single FIGURE is an elevational View, partly in section, of a suspension insulator unit embodying the invention.

Referring now to the drawing, the insulator unit comprises a porcelain body 1 having a crown portion 1a and a metal cap 3 surrounding the crown portion and secured thereto by cement material 4. The upper portion of cap 3 has a slotted socket 311 for receiving and interlocking with the lower ball end of the pin of the next upper insulator unit (not shown), as is conventional in the art. Cap 3 is also formed with an aperture 3b for receiving a cotter pin 30 or the like which prevents in known manner separation of the pin and socket assembly. Porcelain body 1 has a recess 1b on its underside into which steel pin 5 extends and is held therein by cement 6, such as Portland cement, which surrounds the upper cob end 5a of the pin and the portion adjacent thereto. Pin 5 extends outwardly of cement surface 6a so that ball end 5!) of the pin projects beyond the skirt portion 10 of porcelain body 1 as shown. Preferably, the surfaces of recess lb and crown portion 1a are suitably roughened, such as by the application of sand particles thereto by procedures well known in the art, so as to provide an effective bond with the cement.

In accordance with the invention, a collar 7 composed of lead, and having a configuration as more particularly described below and shown on the drawing, overlies the shank of pin 5 in intimate bond therewith from a point just below the inwardly tapered cob end portion 5a to a point substantially below surface 6a of cement mass 6, the pin shank under lead collar 7 being shown in dotted lines.

The portion of lead collar 7 lying embedded in cement 6 is formed with a circumferential groove 711 having sides sloping at an angle of about 45 to a plane normal to the pin axis, the collar being sufliciently thick and the groove therein being sufficiently deep to provide a substantial bearing surface area of the groove in contact with cement mass 6. The embedded end of collar 7 is tapered, as shown, with its slope also being at an angle of 45 to a plane normal to the pin axis. in a typical pin of the above-described construction, the shank of the pin has a diameter of /s inch, the outer diameter of lead collar is 1 inch, and the diameter of the collar at the bottom of the groove is /4 inch.

By virtue of the described collar construction, its lead composition, and the arrangement of the collar with the grooved upper portion in the cement mass and with its lower end extending a substantial distance along the pin shank below current surface 611, there is simultaneously provided protection for pin 5 from corrosion effects as previously described and protection for porcelain body 1 from impacts on and transmitted by the pin. By separating the exposed pin surface substantial distance from cement surface 60 by means of lead collar 7 as shown, direct contact between pin 5 and cement 6 at a point of high leakage current density (and consequent severe corrosive action) is avoided. By virtue of its grooved surface area and the ductile nature of the lead collar, any impact forces on the ball end 5!) of the pin are not only damped appreciably be fore reaching the rigid cement and porcelain, but also are distributed and dispersed over a greater surface area and directed in a large part toward the sides of the pin aperture and away from the upper end of the pin, where such stresses would otherwise be concentrated. As a result, the porcelain insulator unit has higher impact strength. A further advantage is that the grooved collar area 7a provides increased bearing surface for more uniform distribution of the load to the porcelain body when the insulator is subjected to tensile load.

A suitable process which may be used for providing the pin and collar assembly of the invention comprises heating a galvanized pin to about 4G050(i F, the area to receive the lead collar is then dipped into a flux, and the pin is tinned in the collar region. The pin is then placed into a split-type mold having a cavity configuration corresponding to the shape of the collar as shown and described, and molten lead is poured into the mold and solidified to form the collar, after which the mold is removed. This process ell ectively bonds the lead collar to the galvanized steel pin so that the lead will deform before the bond breaks when a force is applied.

A series of tests were carried out to demonstrate the improvement afforded in impact resistance by the grooved lead collar of the present invention. in these tests three groups of insulator units were employed, group A having steel pins with grooved lead collars as above described, group B having pins with ungrooved lead collars, and group C having pins with no collars. in these tests, a. -pound weight was dropped onto the end of each pin from varying heights, and thereafter a voltage of 80 kv. Was applied to the insulator units to determine whether any damage was done by such impacts. As a result of these tests, it was found that the group C units with no collars had an average impact strength of 157 inch/pounds, and group B units with ungrooved lead collars had an average impact strength of 165 inch/ pounds. in marked contrast to these samples, the units of group A with grooved lead collars had an average impact strength of 270 inch/pounds, showing an improvement of about 72% and 63%, respectively, over the other two groups.

There is thus provided by extremely simple and inexpensive means a combination of several advantages in an improved suspension insulator unit, namely, prevent ing corrosion of the steel pin which would cause it to fail, avoiding build-up of corrosion products of the pin which would lead to breakage of the porcelain components of the unit, significantly increasing the impact strength of the insulator, and improving the load distribution on the porcelain component.

While the present invention. has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Therefore, the appended claims are intended to cover all such equivalent variations as come within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A suspension insulator comprising a ceramic dielectric member having a recess, a metal pin extending at one end into said recess and joined therein to said ceramic dielectric member by rigid cement material occupying said recess, said pin projecting outwardly of said recess beyond the surface of said cement material, said pin having a lead collar thereon extending from within said recess outwardly substantially beyond the surface of said cement material, said lead collar having a circumferential groove therein in the portion thereof embedded in said cement material.

2. A suspension insulator comprising a ceramic di electric member having a recess, a metal pin extending at one end into said recess and joined therein to said ceramic dielectric member by rigid cement material occupying said recess, said pin projecting outwardly of said recess beyond the surface of said cement material, said pin having a lead collar thereon extending from a portion of the pin lying in said recess to a portion of the pin substantially beyond the surface of said cement material, said lead collar having a circumferential groove therein in the portion thereof embedded in said cement material, the end of said lead collar within said recess being tapered.

3. A suspension insulator comprising a ceramic dielectric member having a recess, a metal pin extending at one end into said recess and joined therein to said ceramic dielectric member by rigid cement material occupying said recess, said pin projecting outwardly of said recess beyond the surface of said cement material, said pin having a lead collar thereon extending from a portion of the pin lying in said recess to a portion of the pin substantially beyond the surface of said cement material, said lead collar having a circumferential groove therein in the portion thereof embedded in said cement material, said groove having sides sloping at an angle of about 45 to a plane normal to the axis of said pin.

4. A suspension insulator comprising a ceramic dielectric member having a recess, a metal pin extending at one end into said recess joined therein to said ceramic dielectric member by rigid cement material occupying said recess, said pin projecting outwardly of said recess beyond the surface of said cement material, said pin having a lead collar thereon extending from a portion of the pin lying in said recess to a portion of the pin substantially beyond the surface of said cement material, said lead collar having a circumferential groove therein and a tapered end in the portion thereof embedded in said cement material, said groove and said tapered end of said lead collar having sides sloping at an angle of about 45 to a plane normal to the axis of said pin.

References Cited in the file of this patent UNITED STATES PATENTS 1,645,447 Peck Oct. 11, 1927 2,096,613 Hill Oct. 19, 1937 FOREIGN PATENTS 515,914 Germany Jan. 15, 1931 88,144 Sweden Dec. 22, 1936 1,243,481 France Sept. 5, 1960 

